1. Field of the Invention
The present invention relates to a vehicle monitoring system which selectively displays an appropriate image signal out of a plurality of image signals in accordance with the vehicle's condition, the operating condition of various switches and so on.
2. Description of the Related Art
As the vehicle monitoring system which is capable of selectively displaying a number of images on a monitoring unit on the vehicle, there are known a displaying apparatus of Japanese Unexamined Patent Publication (kokai) No. 8-292718 on one hand, and a television apparatus having a backward monitoring function of Japanese Unexamined Utility Model Publication (kokai) No. 6-74499 on the other hand.
FIG. 1 shows the former displaying apparatus disclosed in Japanese Unexamined Patent Publication (kokai) No. 8-292718. In the shown apparatus 101, a GPS (global positioning system) unit detecting part 102 detects whether a monitor 103 is installed on a vehicle or not. On condition that the monitor 103 is installed in a position visible to a driver and when the vehicle's traveling is detected by a parking brake detecting part 104, a CPU 105 allows the monitor 103 so as not to display TV (television) video signal generated from a TV tuner 106. On the other hand, the CPU 105 allows the monitor 103 to display the geographic information loaded from a CD (compact disc) ROM 108 set in a CD driving part 107, such as a CD player, the present positional information obtained by a GPS part 109, etc. in order to ensure the driver's safety during the vehicle's traveling.
While, if it is detected that the monitor 103 is installed in a position invisible to the driver, by the GPS unit detecting part 102, the CPU 105 withdraws the prohibition against the monitor's displaying, so that the TV video signal produced from the TV tuner 106 is displayed on the monitor 103 in spite of vehicle's traveling. That is, depending on the position of the monitor 103 installed, it may be carried out to automatically withdraw the "safety" countermeasure where the monitor 103 is prohibited from displaying any image but a driving map during the vehicle's traveling. In other words, the above-mentioned apparatus is adapted so as to permit the monitor 103 to display the images besides the driving map only when the safety for the driver is ensured.
However, the so-constructed displaying apparatus 101 has a problem as follows. That is, in the apparatus 101, the GPS unit detecting part 102 does detect the installed condition of the monitor 103, while the parking brake detecting part 104 detects whether the vehicle is at a standstill. On the basis of these detection results, the apparatus 101 does restrict the sorts of images capable of being displayed by the monitor. Therefore, when carrying out the selecting of images employing other detection results except for the above-mentioned detection results, for example a position of gear (transmission), an engine rotating speed, or the like, the whole system has to be reconstructed newly.
Thus, there is a problem that the above-mentioned displaying apparatus 101 cannot be used as a so-called "backward monitoring system" which is usable when the vehicle travels in a backward direction.
FIG. 2 shows the latter television apparatus equipped with the backward monitoring function, disclosed in Japanese Unexamined Utility Model Publication (kokai) No. 6-74499. In the shown apparatus 111, when a gear shifting lever occupies other positions besides the backward position while a switch 112 is at an OFF position, the broadcasting signal received by an antenna 113 is fed to a television receiver 114 to display the contents of TV broadcasting.
On the other hand, when the gear shifting lever occupies the backward position and the switch 112 is at an ON position, a power source is supplied to a TV camera 115 for backward monitoring installed in a rear spoiler of the vehicle, so that a video signal of the rear view of the vehicle is introduced to the television receiver 114 to display the rear image. Thus, the television receiver 114, which outputs TV programs when switch 112 is in the OFF position is used as a backward monitoring device for displaying the rear view of the vehicle when switch 112 is at the ON position.
However, the so-constructed television apparatus 111 has a fundamental problem that unless the apparatus is provided with the TV camera 115 for picking up the rear view, no image could be displayed on the television receiver 114.
Additionally, the above-mentioned displaying apparatus 101 and the television apparatus 111 have the following common problem. That is, since it is executed to display the specified picture on the monitor 103 or the TV receiver 114 while prohibiting to display the other pictures on the basis of judgment whether the parking brake is in the activated condition in the displaying apparatus 101 or whether the gear shifting lever occupies the backward position in the television apparatus 111, it is impossible to display an emergency picture expressing the contents of abnormal condition in case that the vehicle is brought into the abnormal condition.